Process and apparatus for the production of a fuse

ABSTRACT

The present disclosure is directed to a method and apparatus for manufacturing a fuse containing a very fine, dust-like explosive wherein at least one thread is guided through the explosive to facilitate the introduction of said explosive into the fuse casing.

United States Patent Rohde et al.

[ 1 Aug. 15, 1972 PROCESS AND APPARATUS FOR THE PRODUCTION OF A FUSEInventors: Wilhelm Rohde; Werner Helfgen,

both of Troisdorf, Germany Dynamit Nobel AG, Troisdorf, Germany Filed:May 1, 1970 Appl. No.: 33,684

Assignee:

Foreign Application Priority Data May 2, 1969 Germany ..P 19 22 374.6

US. Cl. ..86/] R Int. Cl. ..F42b 33/10, C06c 5/08 Field of Search ..86/1; 102/27 [56] References Cited UNITED STATES PATENTS 1,705,360 3/ 1929Fritzsche ..102/27 R 3,155,038 11/1964 Smith 102/27 R 3,435,764 4/ 1969Kelly et al. ..102/27 R Primary Examiner-Benjmain A. Borchelt AssistantExaminer-J. J. Devitt Attorney-Craig, Antonelli and Hill [57] ABSTRACTThe present disclosure is directed to a method and apparatus formanufacturing a fuse containing a very fine, dust-like explosive whereinat least one thread is guided through the explosive to facilitate theintroduction of said explosive into the fuse casing.

25 Claims, 2 Drawing Figures PATENTEDAUB 15 I972 3.683, 742

FIGI

FIG. 2

INVENTORS WILHELM ROHDE WERNER HELFGEN ATTORNEYS PROCESS AND APPARATUSFOR THE PRODUCTION OF A FUSE BACKGROUND OF THE INVENTION The presentinvention relates to a process and apparatus for the manufacture of afuse with a very finegranular or powdery explosive.

Fuses, as is well known, are used for the communication of detonationsto far removed detonable systems. These fuses exhibit, in a sheath, orso-called casing, a continuous explosive core for propagating theinitiating pulse. Depending on the type of the explosive employed andits compression (compacting), a corresponding propagation velocity ofthe initiating pulse can be obtained. The reliability with which thedetonation is completed depends, among other things, on the graindiameter and the amount of the explosive employed, as well as on thediameter of the fuse. Furthermore, the type and construction of thecasing of the explosive core are of importance for the advantageousutilization of the explosive properties of the charge.

It has been known for a long time to employ fuses containing explosivetrinitrotoluene and a lead pipe as the casing. In the manufacture ofsaid fuses, the explosive-filled lead pipe, which initially exhibits arelatively large diameter, is successively drawn through a number ofdrawing dies of respectively decreasing inside cross sections, untilfinally, with a corresponding elongation, the desired small diameter ofthe detonating fuse is obtained. However, this process is associatedwith various disadvantages, for example, the high weight of the leadpipe, and the brittleness of said pipe at low temperatures. This resultsin breakage, and a discontinuous production of fuses of limited length.

Also, another process for producing a fuse having a reduced explosivecontent, wherein the explosive is surrounded with a compact casing of athermoplastic synthetic material, exhibits considerable disadvantages.In this conventional process, there are many moments of danger duringthe manufacture of the fuse, since the explosive is introduced directlybehind an annular die into the still hot plastic hose extrudedcontinuously from the die.

After desensitized mercury fulminate, penthrite, Hexogen (Cyclonite),and similar explosives became popular for fuse manufacture, the practicewas altered to surrounding a granular explosive core with spun textileand/or natural and/or synthetic fibers. In this process, the explosiveis introduced from a feeding funnel into a thin strip of paper,synthetic material, or other suitable substances which is continuouslywound in a helically overlapping fashion at the lower end of the feedingfunnel. This explosive-filled strip is then helically surrounded byvarious layers of wound or spun textile threads twined from fibers, orlike materials. Depending on what is desired or required, particularlywith respect to moisture protection, the thus-obtained fuse can thenadditionally be provided with a coating of varnish, thermoplasticsynthetic material, or the like. For protection against mechanicaldamage, the fuse may optionally also be provided with a widemesh spunenvelope of metallic wires.

However, in addition to the quality of the casing, the type and shape ofthe explosive employed plays an essential part in connection with thequality of the fuse from the viewpoint of explosive technique, and thereliability of complete detonation of the fuse.

In the manufacture of the fuses with continuously woven sheaths, thecentral problem of a unifonn introduction of the explosive into thesheaths presents itself. In these woven (knitted, cloth-type) fuses,pentaerythritol tetranitrate (penthrite) is usually employed as theexplosive, but other high explosives are also usable, such as Hexogen(trimethylene trinitramine), mannitol hexanitrate, and similarsubstances. In case the explosive is present in a granular shape, asatisfactory fluidity and thus a uniform introduction of the explosiveinto the sheath are ensured. However, in case of an extremely smallgranular size of the explosive, i.e., in dust form, for example, whenabout percent of the powder exhibits a grain diameter of smaller thanabout 0.1 mm., the uniform flow of the explosive, which is so importantfor ensuring a reliable complete detonation is no longer achieved, sincethe fluidity of the explosive is insufficient. An irregularly filledfuse results in fluctuating detonating velocities and also in aninterruption of the detonation itself.

On the other hand, it is known that a fuse having a core of an explosivein an extremely fine, dust-like phase, for example extremely finepenthrite, is superior, with respect to explosive (detonating) qualityand with respect to reliable and complete detonation when compared to anexplosive core composed of a granular, fluid explosive, since the formerexhibits more satisfactory detonating propagation properties.

Various methods are known, wherein dust-like explosive, for example,penthrite, are introduced into a preformed sheath. One method resides inintroducing dust-like penthrite in the form of a slurry, or by flushing,and another method consists in trickling (flowing) granular penthritedust into the sheath. However, these methods require additionalcomplicated operating steps during the manufacturing process. In theslurry method, the explosive dust is moistened and flushed into thesheath of the fuse in a wet condition. After the crude fuse has beenproduced, it is dried. Thus, two time-consuming, complicated operatingsteps are involved. When using extremely fine penthrite, in granularform, a granulating process with all secondary operating steps mustfirst be conducted for the dustlike explosive. In this manner, a fluid,granular penthrite dust is obtained. This method is likewise expensiveand complicated.

SUMMARY OF THE INVENTION An object of the present invention is toprovide an improved process and apparatus for producing a fusecontaining a very fine powdery explosive.

Another object of the present invention is to provide a process andapparatus for forming an explosive core for a fuse, made of a veryfine-grained or dust'like, dry explosive, for example pentaerythritoltetranitrate (extremely fine penthrite) or extremely fine hexogen. Theexplosive is enclosed is a spun or braided sheath.

A further object of the present invention is to provide an improvedprocess and apparatus for producing a fuse which substantiallyeliminates the uncertainties inherent in the use of fuses containinggranular explosives.

Still another object of the present invention is to provide an improvedprocess and apparatus for the manufacture of a detonating fuse whichuses an explosive which does not exhibit any fluidity in its solidphase.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

The present invention is directed to a process and apparatus for themanufacture of a fuse having a very fine-grained or dust-like explosive,wherein the explosive is introduced from a filling funnel into a sheathcontinuously manufactured at the lower end of the funnel. According tothe present invention, at least one thread, deflected from the verticalaxis of the feeding funnel (feed hopper) is guided through the feedingfunnel preferably in a circular direction and continuously introducedinto the sheath at the end of the feeding funnel, together with theexplosive. Because of the constant motion of the thread running throughthe feeding funnel, eccentric with respect to the vertical axis, thecone of explosive is continuously cut, and the explosive dust can beuniformly fed through the funnel due to its inherent weight. In thismanner, it is possible for the first time to employ very fine-grainedand dust-like explosive, such as penthrite, which is extremely fine, inits natural, dry form, without any preliminary and/or post treatment,for the formation of a uniform explosive core. By means of the processand apparatus of the present invention, any desired amount of charge,i.e., explosive weight per 1 meter of fuse, as required by the blastingoperation, can be provided. The process and apparatus of the presentinvention is suitable for the manufacture of low-energy fuses, used, forexample, as detonating fuses for base detonation or in areas endangeredby firedamp, with charge amounts of 3 g./m. and, in special cases, ofless than 1 g./m. In these cases, a dust-like explosive, such asextremely fine penthrite, is the only substance which ensures a reliablecomplete detonation of very weak explosive cores, which are required,for example, for the prevention of lateral detonation propagations.

Heavy-weight charges of the explosive core can also be advantageouslyproduced by the process of the present invention. By the use of thethreads, a uniform introduction and a uniform distribution of theexplosive in the explosive core are ensured. Thus, in addition to usingminor amounts of charge of 1 g. per meter of fuse, large amounts ofcharge, up to above about 100 g. per meter of fuse can be realized. Ofcourse, the process of the present invention, developed specifically forthe introduction of very fine-grained explosive material into a fuse canalso be employed in connection with more granular explosives, since thepresent process also promotes the uniform flow of the explosiveparticles into the fuse in these explosives, particularly in case ofhigh loading (charge) weights of the fuse.

According to the present invention, it is possible, by the use ofdust-like explosive, to produce fuses having a substantially reducedexplosive content as compared to fuses utilizing granular, fluidexplosive contents, whereby substantial savings in explosive can beachieved. It is thus possible to reduce the weight of the explosive inthe explosive core up to about 25 or 30 percent, as compared with thepreviously conventional fuses utilizing granular, fluid explosive. Thisis because the dust-like explosive, in connection with such crosssections of the explosive core, will still reliably propagate thedetonation completely in those cases where a granular explosive is notable to provide such a complete propagation. Thus, with a reduction inthe amount of explosive employed, a more favorable manufacturing expensecan be obtained in the production of the explosive fuse.

One example of the thread guidance according to the present invention isthat at least one thread is circularly guided within the feeding funnelat a short distance from the wall of the feeding funnel, so that thecone of explosive present in the feeding funnel continually is being cutclose to its periphery.

The principle developed by the present invention is based on the use ofone or several threads playing the part of a conveying means. This iseffected, according to a further feature of the invention, by rougheningthe thread surface, so that the thread, during its passage through thedry, dust-like explosive, entrains a certain amount of the explosive. Inthis manner, the explosive is conducted into the sheath. One property ofthe thread which facilitates the entrainment of the explosive dust is toprovide the thread with a suitable surface characteristic, i.e., asurface which is more or less roughened, and possesses a concomitantsufficient tensile strength, so that the dust particles adhere to thethread.

According to another feature of the present invention, the thread can bedrawn off from the storage reel under tension. Also, the thread can bemade to vibrate. This is possible, for example, by the selection of asuitable tension for the thread. The vibration of the thread, duringpassage through the funnel filled with explosive dust, sets a certainamount of explosive in motion, depending on the thickness of the thread,the surface characteristics thereof, and the intensity of the vibration,such that the formation of an explosive core about the thread in auniform fashion is promoted.

The motion of the thread in the funnel filled with explosive can beeffected in various ways. One possibility resides in guiding the threadon the circumference of a disk provided between the storage reel and theupper opening of the feeding funnel. One embodiment of the presentinvention provides that the thread is clamped to the circumference ofthe disk, or is guided in an eyelet or a similar means, and is set intomotion by the rotation of the disk. However, it is just as effective tohave the thread rotate about a stationary disk disposed between thestorage reel and the upper opening of the feeding funnel. However, it islikewise possible to set the thread into circular motion by means of acam gear. Also, a reciprocatory motion of the disk arranged between thestorage reel and the upper opening of the feeding funnel in the verticaldirection promotes the uniform feeding of the explosive. This motion canbe superimposed, for example, by a circular motion of the thread.

Another embodiment of the process of the present invention suggestssetting the thread into circular motion by pulling the thread off from avertically arranged yarn reel (spool) and superimposing on this motion asecond motion, preferably circular, by moving the yarn reel holder ofthe yarn reel.

The threads which can be employed are generally twisted from shortfibers, such as for example synthetic fibers, natural fibers, ormixtures of natural and synthetic fibers. Thus, the synthetic fibers canbe mixed with cell wool, wool, flax, and the like.

DESCRIPTION OF THE DRAWINGS The present invention will become more fullyunderstood from the detailed description given hereinbelow and theaccompanying drawings which are given by way of illustration only andthus are not limitative of the present invention and wherein,

FIG. 1 shows a schematic structure illustrating a process for producinga detonating fuse; and

FIG. 2 shows a modification of the process of the present invention witha superimposed motion of the thread.

DESCRIPTION OF THE PREFERRED EMBODIMENT The manufacture of a fuse withan explosive core of a dust-like explosive, for example pentrhite,wherein 80 percent of the explosive exhibits a grain diameter of smallerthan about 0.l mm. and thus no longer possess fluidity, is conducted onthe schematically shown spinning apparatus. The hose 9 of said apparatusis made of natural and/or synthetic fibers which is continuously wovenand envelopes the explosive core 8.

The dust-like penthrite 1 is contained in a funnel 2 disposed above thespinning plane 7 of the device. Above the funnel 2, the rotatingcircular disk 5 is provided, the thread 4 being guided over the rimthereof in such a manner that it passes a short distance, for example,only about a few millimeters, from the inner wall of the funnel andextends out of the lower end of the funnel. The storage reel of thethread 4 is attached, in the illustrated example, on the rotating disk 5by means of the reel holder 6. In this manner, it is ensured that thethread 4 executes a circular motion, and cuts the cone of explosive l inthe funnel 2 continuously at its periphery so that the explosive dustcan be continuously uniformly replenished, due to its inherent weight.The thread 4 is guided, between the reel holder 6 and the explosive core8 surrounded by the hose 9, over the circumference of the disk 5 in sucha manner that it is under such tension that it is set into slightvibration during the circular guiding procedure. By using this system,it is ensured that the thread 4 entrains a constantly uniform amount ofpenthrite dust from the funnel 2. Upon exiting from the lower end of thefunnel 2, the explosive core (thread 4 plus penthrite) is surrounded bya film strip 3 of paper, a synthetic material, or another suitablematerial. This can be achieved by winding at least one of said materialsaround the core.

Depending on the requirements to be met by the detonating fuse, completefreedom can be used in surrounding the fuse core, produced according tothe present process, with an explosive core of a very finegrained ordust-like explosive, and with additional external casings of all types.

In the process of the present invention, other devices, for example, camgears or similar means, can also be used, by means of which the thread 4can be guided within the funnel 2 in the desired manner.

FIG. 2 shows a variation of the process of the present invention for theproduction of a fuse with an explosive core of a dry, very fine-granularor dust-like explosive, operating with refined methods. Two or more arms11 utilized for receiving the yarn reels 10 are provided insubstantially vertical alignment at the reel holder 6, said reel holderbeing mounted so that it rotates about its longitudinal axis. By drawingthe thread 4 ofi the yarn reels l0, movably disposed on the arms 11 ofthe reel holder 6, the thread 4 executes a circular motion about thedisk 5 which is connected in a fixed manner with the reel holder 6 andis disposed between the lower end of the yarn reel 10 and the feedingfunnel 2. In addition to this motion of the thread 4, another circularmotion is superimposed by a slow rotation of the reel holder 6 about itslongitudinal axis. In this manner, the continuous, uniform cutting ofthe cone of explosive l by the threads 4 is ensured, and detonatingfuses of any desired amount of charge, i.e., weight of explosive permeter of fuse, can be manufactured.

Any desired other ways of guidance of the thread, including pendulatingones, are possible within the scope of the present invention, in orderto convey the nonfluid substance out of the feeding funnel 2 in anydesired, but always uniform and constant, amount.

The yarns from which the hose 9 is woven comprise cellulose fibers, cellwool (synthetic wool), nylon, Perlon, rayon, Dralon (polyacrylic fiber),wires of ductile metals, polycarbonates, polyesters,polytetrafluorethylene, and the like.

Suitable threads 4 which can be used in the present invention includethreads of wool, cell wool, flax hemp, and the like. Synthetic fibersare generally unsuitable due to their character, since they exhibit toosmooth a surface. However, if the surfaces of synthetic fibers can beappropriately roughened, said fibers are also useable.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention and all suchmodifications as would be apparant to one skilled in the art areintended to be included.

It is claimed:

1. A method for manufacturirig a fuse containing a very fine, dust-likeexplosive which comprises introducing the explosive from a feeding meansinto a casing disposed at the discharge end of said feeding means,wherein at least one thread having a roughened surface is deflected fromthe vertical axis of the feeding means, is guided under tension throughthe feeding means containing the explosive and is continuouslyintroduced into the casing, together with the explosive, at saiddischarge end of the feeding means, and wherein amounts of the explosiveare entrained in the surface of the thread during the passage of thethread through the feeding means into the casing.

2. The method of claim 1 wherein about percent of the explosivepossesses a grain diameter less than about 0. 1 mm.

3. The method of claim 1, wherein the casing is being continuouslymanufactured at the lower end of the feeding means.

4. The method of claim 1 wherein the thread is introduced into thefeeding means and is guided in a circular manner through said feedingmeans.

5. The method of claim 1 wherein the feeding means is a feeding funneland the thread is guided in a circular manner through the explosivecontained in the feeding funnel and in close proximity to the wall ofsaid funnel so that the cone of explosive present in the feeding funnelis continually cut in the proximity of its periphery.

6. The method of claim 1 wherein the thread is made to vibrate.

7. The method of claim 1 wherein the thread is guided on thecircumference of a disk disposed above the upper opening of the feedingmeans.

8. The method of claim 1 wherein the thread is attached to thecircumference of a disk and is set into motion by the rotation of thedisk.

9. The method of claim 7 wherein the disk reciprocates in the verticaldirection.

10. The method of claim 1 wherein the thread is set into circular motionby means of a cam gear.

1 l. The method of claim 1 wherein the thread is set into a firstcircular motion by being drawn from a vertically disposed yarn reel, anda second circular motion is superimposed on said first motion by themovement of the holder of the yarn reel.

12. The method of claim 1 wherein the thread is twisted from shortfibers of synthetic or natural fibers or mixtures thereof.

13. The method of claim 11 wherein two threads are introduced intodifferent portions of the feeding means containing the explosivematerial.

14. The method of claim 1 wherein the explosive is selected from thegroup consisting of pentaerythritol tetranitrate, trimethylenetrinatramine, and mannitol hexanitrate.

15. The method of claim 1 wherein the explosive in an amount of about 1to 100 grams per meter of fuse is introduced into the sheath of saidfuse.

16. The method of claim 1, wherein the thread has a smooth surface andincluding the step of roughening the surface of the thread to enable theentrainment of amounts of the explosive in the surface of the thread.

17. An apparatus for manufacturing a fuse which comprises a feedingmeans adapted to contain an explosive material, deflecting means forintroducing at least one thread, which is deflected from the verticalaxis of the feeding means into said feeding means, and means for guidingthe thread through the feeding means and continuously introducing theexplosive plus the thread into the casing at the discharge end of thefeeding means, the thread being provided with a roughened surface forentraining amounts of the explosive during its movement through thefeeding means and into the casing.

18. The apparatus of claim 17 wherein spinning means are provided forcontinuously manufacturing the casing.

19. The apparatus of claim 17 wherein the deflecting means is a circulardisk disposed above the feeding means and storage reel means areprovided for conveying the thread over the periphery of said disk andintroducing it into the feeding means.

20. The apparatus of claim 19 wherein means are provided for rotatingthe disk.

21. The apparatus of claim 19 wherein the storage reel means containingthe thread is attached to the top i f e apparatus of claim 17 whereinthe deflecting means is a cam gear.

23. The apparatus of claim 17 wherein the deflecting means are twocircular disks, each of which communicate with rotatable storage reels.

24. The apparatus of claim 20 wherein the rotatable storage reelscommunicate with a rotatable reel holder, and means are provided forrotating the rotatable storage reels and the rotatable reel holder.

25. The apparatus of claim 17 including means for vibrating the threadduring its passage through the feeding means and into the casing.

1. A omethod for manufacturing a fuse containing a very fine, dust-likeexplosive which comprises introducing the explosive from a feeding meansinto a casing disposed at the discharge end of said feeding means,wherein at least one thread having a roughened surface is deflected fromthe vertical axis of the feeding means, is guided under tension throughthe feeding means containing the explosive and is continuouslyintroduced into the casing, together with the explosive, at saiddischarge end of the feeding means, and wherein amounts of the explosiveare entrained in the surface of the thread during the passage of thethread through the feeding means into the casing.
 2. The method of claim1 wherein about 80 percent of the explosive possesses a grain diameterless than about 0.1 mm.
 3. The method of claim 1, wherein the casing isbeing continuously manufactured at the lower end of the feeding means.4. The method of claim 1 wherein the thread is introduced into thefeeding means and is guided in a circular manner through said feedingmeans.
 5. The method of claim 1 wherein the feeding means is a feedingfunnel and the thread is guided in a circular manner through theexplosive contained in the feeding funnel and in close proximity to thewall of said funnel so that the cone of explosive present in the feedingfunnel is continually cut in the proximity of its periphery.
 6. Themethod of claim 1 wherein the thread is made to vibrate.
 7. The methodof claim 1 wherein the thread is guided on the circumference of a diskdisposed above the upper opening of the feeding means.
 8. The method ofclaim 1 wherein the thread is attached to the circumference of a diskand is set into motion by the rotation of the disk.
 9. The method ofclaim 7 wherein the disk reciprocates in the vertical direction.
 10. Themethod of claim 1 wherein the thread is set into circular motion bymeans of a cam gear.
 11. The method of claim 1 wherein the thread is setinto a first circular motion by being drawn from a vertically disposedyarn reel, and a second circular motion is superimposed on said firstmotion by the movement of the holder of the yarn reel.
 12. The method ofclaim 1 wherein the thread is twisted from short fibers of synthetic ornatural fibers or mixtures thereof.
 13. The method of claim 11 whereintwo threads are introduced into different portions of the feeding meanscontaining the explosive material.
 14. The method of claim 1 wherein theexplosive is selected from the group consisting of pentaerythritoltetranitrate, trimethylene trinatramine, and mannitol hexanitrate. 15.The method of claim 1 wherein the explosive in an amount of about 1 to100 grams per meter of fuse is introduced into the sheath of said fuse.16. The method of claim 1, wherein the thread has a smooth surface andincluding the step of roughening the surface of the thread to enable theentrainment of amounts of the explosive in the surface of the thread.17. An apparatus for manufacturing a fuse which comprises a feedingmeans adapted to contain an explosive material, deflecting means forintroducing at least one thread, which is deflected from the verticalaxis of the feeding means into said feeding means, and means for guidingthe thread through the feeding means and continuously introducing theexplosive plus the thread into the casing at the discharge end of thefeeding means, the thread being provided with a roughened surface forentraining amounts of the explosive during its movement through thefeeding means and into the casing.
 18. The apparatus of claim 17 whereinspinning means are provided for continuously manufacturing the casing.19. The apparatus of claim 17 wherein the deflecting means is a circulardisk disposed above the feeding means and storage reel means areprovided for conveying the thread over the periphery of said disk andintroducing it into the feeding means.
 20. The apparatus of claim 19wherein means are provided for rotatiNg the disk.
 21. The apparatus ofclaim 19 wherein the storage reel means containing the thread isattached to the top of the disk.
 22. The apparatus of claim 17 whereinthe deflecting means is a cam gear.
 23. The apparatus of claim 17wherein the deflecting means are two circular disks, each of whichcommunicate with rotatable storage reels.
 24. The apparatus of claim 20wherein the rotatable storage reels communicate with a rotatable reelholder, and means are provided for rotating the rotatable storage reelsand the rotatable reel holder.
 25. The apparatus of claim 17 includingmeans for vibrating the thread during its passage through the feedingmeans and into the casing.